The inventive concepts described herein relate to semiconductor memory devices, and more particularly, relate to memory systems and methods of operating memory controllers.
A semiconductor memory device is a memory device that may be fabricated using semiconductors such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), indium phosphide (InP), and so on. Semiconductor memory devices are classified into volatile memory devices and nonvolatile memory devices.
Volatile memory devices may lose stored contents at power-off. Volatile memory devices may include a static RAM (SRAM), a dynamic RAM (DRAM), a synchronous DRAM (SDRAM), and the like. Nonvolatile memory devices may retain stored contents even at power-off and may include a read only memory (ROM), a programmable ROM (PROM), an electrically programmable ROM (EPROM), an electrically erasable and programmable ROM (EEPROM), a flash memory device, a phase-change RAM (PRAM), a magnetic RAM (MRAM), a resistive RAM (RRAM), a ferroelectric RAM (FRAM), and so on.
A semiconductor memory may experience sudden power-off (SPO). The SPO may be such a phenomenon that a power supplied to the semiconductor memory is blocked without warning due to power failure and/or separation of a power plug. The SPO may cause an abnormal operation of the semiconductor memory. Thus, preparing for the SPO may improve the reliability of the semiconductor memory.